Radio apparatus



April 9, 1929. G. w. PlCK'ARD 1,708,453

RADIO APPARATUS Filed Sept 29, 1925 I 2 sheets-sheet 2 IN VENTOR Patented Apr. 9, 1929.

UNITED STATES PATENT OFFICE.

GREENLEAF WHITTIER PICKARD', OF NEWTON CENTER, MASSACHUSETTS, ASSIGNOR TO WIRELESS SPECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A

CORPORATION OF NEW YORK.

RADIO APPARATUS.

Application filed September '29, 1923. Serial No. 865,528.

This invention relates to radio apparatuswherein condenser C forms a part of the more particularly of. the type whereln the closedcircuit tuned by it and including the form of receiving apparatus, substantlally all ad ustabIe secondary coil of an oscillation the devices are enclosed in and attached to a transformer T, the

rimary and secondary of 6 box or cabinet N having terminals, binding which have a variable coupling, the two coils posts or connecting points for the connection constituting a coupling between the clowd of aerial conductors which intercept the circuit of condenser O and the open grounded transmitted waves.

The object of the invention is to provide circuit of the antenna A-E; and in the antenna clrcuit is preferably a variable tuning such a receiving set with means convenient to condenser AC. The portion of the antenna to the purchaser and user for operating the set the right of binding posts A, A, and includby various aerials.

ing condenser AC and the primary of trans- The invention consists of the improvements former T, forms a part of the receiving set described and pointed out in the claims beitself inside cabinet N; and to binding posts 7 15 low, and shown in the drawings, which are di- A A is connected any desired unded l rb m loop agrammatic and of which 0 en or Marconi antenna A--E.-

Figure 1 is an illustration of one embodibinding posts L a lead 20 is taken to a switch ment of the invention Fig. 2 is an illustration of another embodiment; and

point 2; and from loop binding post 'L is denser G. A switch S is connected via a lead Fig. 3 is an illustration of a preferred em- 30 to the other side of condenser C. In the I bodiment.

position of switch S shown in full lines, con- The invention in its preferred form is detacting'with switch point 2, the variable consigned to permit the user of the receivin set denser C is connected in the circuit of the to use either a small or a lar e grounde anloop to which terminals L, L are'adapted to eissue Patent be connected, so that condenser C ma serve 11,913) without change of calibration of the as the necessary tuning condenser or the antenna tuning condenser, and to permit the loop, as explained in my said patent. One user to employ at will with his receiving set end of the secondary of transformer T is coneither of the now well-known forms of serials nected to a second switch point 1 of switch S; i.- e., the grounded antenna of said Marconi and in the position of switch S shown in dottype or the ungrounded closed loop or coil ted lines, contacting with switch point 1 conaerial of my Patent 876,996, without change denser C is included in the secondary circuit of tuning condenser; that is, permittin the of antenna AE,sothat the user may employ tennaof the Marconi type R type of aerial.

In Fig. 1, the dot and dash rectangle repre- I se'nts a cabinet N enclosing the apparatus have both antenna A-E an with the exception of the aerials, the cabinet simultaneously connected carrying connecting points or binding posts A A for a grounded Marconi aerialAE, points or binding posts L L ungrounded condenser-tuned and connectin for my closed loop aerial L.

The common tuning aerial systems of difierent t condenser for these is at C shown from binding as associated in a common a'shion with the to the full line position shown. This will enbe better in pracof the antenna 'tch S is moved eggs eyed isnot of the taken a lead 10 to oneside of tuning conlocal receiving apparatus, including a thersure against interferenceb undesired signals mionic tube or other detector U and a transwlth the reception to be 0 tamed by way of former R, which couples said tube with areloop L, which interference otherwise mlgb ceiving telephone or additional amplifying affect the receiving a paratus U, R, etc.,

oundedaerial or antenna sysway of transformer tubes. The

Y and by way of the vatem, with w ich variable tunin condenser rious' electrostatic couplings, even including C is associated, is shown in pre rred form, r the portion of, the antenna secondary circuit opened b switch S. By such an arrangement as the above it is made possible for the user to employ at will, with the same tuning condenser, eithertype of aerial, which is very desirable. For the purpose of receiving communications from long distance, he may prefer to use the grounded antenna. But he may prefer to use the loop aerial, either in cases where it is not practicable to provide a grounded antenna, or also for the purpose of assisting in cutting out interference by taking advantage of the directional properties of the loo aerial.

In Fig. 2 is a modified form of apparatus in and on the cabinet N indicated by the dotted line closed rectangle. Herc both the antenna AE and the loop L are connected to the binding posts AL and AL on the cabinet. The transformer is, indicated as a single coil or auto transformer AT. Two switches S S are shown, operating on a common contact 3 and upon a plurality of.

switch points, as shown, connected to taps along the transformer coil. The common tuning condenser C is shown as having one side connected to switch S and the other to binding post ALF, and both sides connected to the receiving thermionic tube U which is connected to the head-telephones P. When both switches S and S are closed to contact 3, as shown in dotted lines, condenser C is operatively connected in the circuit of loop L, the antenna couplingcoil AT being cut out of circuit. While the upper part A of the antenna may be left connected to post AL while loop L is so connected, yet if the ounded antenna have greater receiving efect than loop L, such as to enable its effect to swamp the effect of the loop, then the antenna lead-in should be removed from 0st AL when the loop is in action. When switch S is open to contact 3 and connected to the switch points leading to coil AT, the apparatus is in condition for normal operation by the antenna AE via coupling coil AT to the closed circuit AT, C, which closed circuit is tunable by condenser C and by the operation of switches S, S over the transformer switch points. In this case, switch S also is moved to connect with the transformer switch points, both switches being in contact with various of the transformer switch points as illustrated in full lines, and disconnected from common switch contact 3. In this con:v

dition of the apparatus, coil AT acts as the coupling coil, for antenna AE, and condenser G acts as the critical tuning element of the secondary circuit including transformer AT. In the form of Fig. 2, it is better to disconnect loop L from binding posts AL and AL if it affords a deleterious inductance in shunt to the antenna tuning coil AT.

Fig. 3 illustrates a modified embodiment of the apparatus in and on the cabinet N shown indotted lines. In this form, the

grounded antenna AE and theloop or coil aerial L both may be lcft'attached to the aerial terminals of the set, and the antenna A E may be either a small indoor grounded antenna or a large outdoor grounded antenna. As in Fig. 1, the antenna is connected to the terminals A, A of the set, and the loop aerial L is connected to terminals L L thereof. Also variable tuning condenser C can be connected in either the secondary of the grounded antenna system or in the loop aerial/system L, at will. As in Fig. 1, the coupling between the grounded antenna and its secondary circuit consists of an inductive transformer T, thevariableantenna tuning condenser AC being in series with the primary coil of this coupling. Switch S controls condenser C as to including it at will in either the antenna system OIillB loop system. Across antenna terminals A A a condenser K is arranged to be connected by a switch W operating on contact point A As is well known, the variable antenna tuning condenser AC is calibrated as a matter of convenience to the user to assist him in adjusting theset to receive from desired distant transvmitters by adjusting the condenser to a point on the scale known to him to give reception from such transmitter. Condenser K has a value in capacity which is equal to the difference of the capacity of a large and small grounded antenna. The user may desire to employ a small indoor grounded antenna (.001 mfd.) or a large outdoor grounded antenna (.003 mfd.) for the same wave length range; although antenna tuning condenser AC usually is calibrated to correspond with the capacity of the ordinary outdoor grounded antenna of dimensions for receiving from entertainment-broadcasting transmitters. When switch Wis closed to contact A a condenser K of the above specified capacity (which in a fraction of a microfarad may be .002) therebyis placed in'shunt to condenser AC and the primary of transformer T, and a small indoor grounded antenna may be em ployed' with the condenser AC calibrated relative to the usual large outdoor grounded antenna. Thus condenser K of such value, and switch W permit use of a small indoor grounded antenna for the same wave length as a large outdoor grounded antenna, without any change of calibration of antenna condenser AC relative to the large antenna. Switch S preferably carries three contacting knife switch blades X, Y and Z, switch S being preferably a triple pole, double throw device. The change of variable tuning condenser C from'an antenna system tuning condenser to a loop system tuning condenser is made by the operation of the switch blade Y from the full line position shown (connecting switch points 3 and 4) to the dotted line position connecting switch points 3 and 7. Switch S may comprise such switch blade Y service, switch S should include blade Z which serves to connect the other side of condenser C (fromthat connected by blade Y) to the antenna secondary and the loo system respectively. Also, switch S prefera ly comprises, in addition to blades Y and/or Z, the blade X arranged with the contact points 1 and 2 to cut out antenna lead-in when condenser C is disconnected from the antenna secondary and connected to the loop system, and to cut in the antenna when condenser C is connected in the closed secondary with the coil of coupling transformer T. It is not necessary to have all four binding posts A A L L, for clearly L may be combined with A As a rule, the antenna lead-in, the wire leading from binding post A to earth E, and

the loop aerial from L to binding posts L L are not furnished with the apparatus assold, which includes only the cabinet N and the local apparatus shown as located therein.

Tuning condenser 0 preferably possesses a sufiicient range of capacity to tune each of the secondary circuit of antenna AE and the loop aerial L to the desired wave lengths; and preferably it has substantially the same wave length range for said two aerials.

Among the advantages of the invention are avoiding the necessity of duplicating variable condenser C for both the antenna secondary circuit and the loop system;-the convenience to the user of being able readily to shift from an antenna aerial AE to a loop aerial L; and the ability to employ difi'erent-sized grounded antenna (by the provision of condenser K and switch W) without changing the calibration of the antenna condenser AC and without the necessity of using a difi'erently calibrated antenna condenser when such different grounded antenna is used.

I claim 1. In a radio communication apparatus, the combination with two independently operating aerials, one of the grounded antenna type and the other of the ungroundedof a closed secondary circuit tunable thereby j connecting points for a grounded antenna and for an ungrounded closed loop aerial; means for couplingthe secondary circult with a grounded open antenna connected to said points; and a switch which in one position closes the antenna circuit, closes the secondary circuit through the condenser and open-circuits the loop, and in another position opens the antenna and the secondary circuit and closes the loop circuit through the condenser.

3. Radio-receiving apparatus which comprises an antenna aerial and a loop aerial constructed to operate independently thereof, an oscillation transformer; a secondary circuit of the antenna-aerial constructed as a resonant circuit and including a variable condenser having substantially the same wave-length range for the antenna aerial as for the loop aerial; and a switch constructed and arranged to open said secondary circuit and connect the loop aerial in parallel with said condenser, and alternately" to disconnect the loop-aerial from the condenser and include the condenser in the secondary circuit of the antenna-aerial.

4. Radio-receiving apparatus which comprises antenna-aerial terminals and loopaerial terminals, an oscillation transformer connected to the antenna terminals; a secondary circuit of said antenna-aerial constructed as a resonant circuit and including -a variable tuning condenser having a sufficient range of capacity to tune either said 'secondary circuit or the loop aerial to decluding a variable condenser having a range of capacity sufiiclent to tune either sald secondary circuit or a loop-aerial to desired wave-lengths; an oscillation transformer coupling said antenna-aerial terminals to said closed resonant circuit; and switching means constructed and arranged to open said closed resonant circuit and connect the loop aerial in parallel with'said condenser, and alternately to open the loop circuit and include the condenser in the secondary circuit of the antenna-aerial.

6. Radio receiving-apparatus which comprises local receiving apparatus; a closed circuit connected to the receiving apparatus;

independently operative antenna and loop aerials; a condenser associated co-operatively with said closed circuit and having a capacity suitable to make the antenna and loop aerials"respeetively resonant to a desired order of wave lengths; and switching means for alternately connecting the antenna aerial and the loop aerial to said condenser, whereby either aerial system at will is made resonant to the desired order of wave-lengths.

7. Radio receiving apparatus including, in combination, the aerial apparatus and a receiving set, the-aerial apparatus including a grounded antenna circuit and a closed loop aerial circuit, said antenna circuit and loop aerial circuit being severally complete and functionally independent of each other, and

thereceiving set including binding posts for the antenna circuit and the loop aerial circuit together with switching means for operatively connecting the receiving set at Will with either the loop circuit or the antenna circuit.

- '8. Radio receiving apparatus, including, in combination, a receiving set and associated antenna and loop circuits; :1 variable tuning condenser in the receiving set t0- gether with connecting points for the antenna circuit and the loop circuit; and switching means for including said tuning condenser efi'ectively in the circuit of the antenna and'the loop alternately at will.

GREENLEAF WHlTTlER PICKARD. 

